Connection nodes in integrated circuits may include one or more bond pads, pins, die terminals, die pads, contact pads, metal junctions, interconnect elements, and so forth. Connection nodes may be used to pass an electrical signal, such as a reference voltage, to one or more circuits. The electrical signal may be used during the normal operation of the one or more circuits. A few examples of connection nodes include nodes that may be used to bypass pump circuitry, nodes that may be used to bias a portion of a circuit, nodes that may be used to pass an input or output signal, and so forth. Some connection nodes are dual-direction in that they are used to pass negative and non-negative electrical signals, such as signals from −6V up to +6V. Among other things, dual-direction connection nodes may allow a broader voltage spectrum to be used in programming an array, such as a memory array, as compared with a single direction node with the same maximum non-negative or maximum negative voltage. Connection nodes may be used in any of a number of apparatuses. As used herein, an apparatus may refer to a number of different things, such as circuitry, a memory device, a memory system (e.g., SSD) or an electronic device or system (e.g., a computer, smart phone, server, etc.).
Connection nodes in integrated circuits, including dual-direction nodes, are sometimes subjected to over-limit electrical conditions such as electrostatic discharge (ESD). One or more protection circuits are often coupled to such dual-direction nodes in order to protect the dual-direction node and circuitry that is coupled to the dual-direction node. Circuitry coupled to a dual-direction node may include active devices such as diodes and bipolar junction transistors (BJTs). This circuitry may need to be protected from, for example, voltages and/or currents associated with ESD events and other over-limit electrical conditions.
Some protection circuits include circuitry that provides a low-impedance conductive path from a node such as a dual-direction node to a reference voltage such as ground and/or to a voltage source such as VCC. The conductive path provides a path to dissipate (e.g., shunt) the current associated with, for example, an ESD event, before the circuitry coupled to the dual-direction node is damaged. Other protection circuits include circuitry that clamps a voltage provided to a dual-direction node.
In designing an adequate protection circuit for a dual-direction node, a turn-on condition such as a turn-on voltage should be sufficiently low to provide protection before other circuitry coupled to the dual-direction node is damaged. Also, the protection circuit should be able to dissipate a sufficient amount of current associated with, for example, an ESD event, as well as be able to clamp a voltage provided to a dual-direction node. A dual-direction node's protection circuit, however, should generally not interfere with the normal operation of other circuitry coupled to the dual-direction node and should not latch up during normal operations. Furthermore, the added capacitance from a protection circuit seen at a dual-direction node may need to be small in high-speed circuits in order to reduce switching delays. Lastly, a protection circuit may need to have a relatively small footprint and have adjustable operating characteristics in some cases.